Smart routers-simple optics: network architecture for IP over WDM

ABSTRACT

A system and method of routing communication signals is provided. A first technique uses a packet switched device that operates using Internet Protocol, the packet switched device determines one or more commands based on a routing request to establish, maintain, restore or breakdown one or more communication paths and a circuit switched device that provides physical switching between a plurality of ports based on the one or more commands from the packet switched device. A second technique for expediting error condition information is also provided. As various error conditions are recognized, information relating to the error conditions is provided directly to the packet switched device to enable the packet switched device to restore communications with minimal delay.

This nonprovisional application claims the benefit of U.S. ProvisionalApplication No. 60/159,038, filed Oct. 12, 1999.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to routing information.

2. Description of Related Art

Current Wavelength Division Multiplexing (WDM) and Internet Protocol(IP) technologies provide capabilities that may be exploited forimproved network operations. Existing circuit switched networks utilizesemi-manual or centralized circuit allocation and standardized fail safescenarios (exemplified by Synchronized Optical Network or SONET) to setup circuits for communications. Other networks use IP to forwardpackets, trusting that the messages will eventually reach theirdestination. Unfortunately, existing IP communications systems sufferfrom a number of inefficiencies such as providing relatively long delaysand slow throughput after a communication is interrupted. New technologyis needed to provide faster communication services.

SUMMARY OF THE INVENTION

The invention provides a method and apparatus for routing information.The smart router-simple optics (SRSO) approach concentrates intelligencefor resource management in an Internet Protocol (IP) device; physicalcross connections are then handled by a circuit switched device.

Thus, an exemplary SRSO router is constructed of multiple ports that arejoined by optical cross connects and an IP router that provides IPfunctionality. The cross connection devices are only responsible forproviding transmission services: signal regeneration, media accesscontrol (MAC) level framing, dynamic local optical connectivity, andphysical transmission. The IP layer provides all complex functions:network optimization including traffic engineering and Quality ofService (QoS), management of optical resources (wavelength management),and restoration.

One exemplary embodiment overcomes the limitations of the known devicesby having the IP device handle addressing, routing and the management oftopology and network resources. The cross connection device then isconcentrated on handling the capacity and reconfigurable optical crossconnects. The IP layer can then control the cross connection layer forexample, through the abstraction of IP tunneling.

Thus, the SRSO approach can be used to distribute the control of acircuit based network. Alternatively, the SRSO approach can be used toimprove the efficiency of a packet based network by providing highbandwidth connections between communications nodes. The high bandwidthconnections are reconfigured to provide bandwidth as required toefficiently manage packet service data.

Another exemplary embodiment corrects communications errors byattempting to correct the error within the communications node,attempting to correct the error by communicating with othercommunications nodes and communicating with the entire network.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the following figures,wherein like numerals designate like elements and wherein:

FIG. 1 is a block diagram of a network system;

FIG. 2 is a block diagram of an exemplary portion of a network with anormal communication path established;

FIG. 3 is another block diagram of an exemplary portion of a networkwith a normal communication path established;

FIG. 4 is a block diagram of an exemplary portion of a network with arestoration communication path established;

FIG. 5 is a block diagram of an exemplary router using an overlaysystem; and

FIG. 6 is a flowchart illustrating an exemplary method of routingcommunication signals.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a block diagram of an exemplary communication system 100. Thecommunication system 100 includes a first data terminal 110 connected toa network 130 through a first data link 112, and a second data terminal120 connected to the network 130 through a second data link 122. Thenetwork 130 can accommodate communication between the first dataterminal 110 and the second data terminal 120 by providing an internalcommunication path capable of transmitting and receiving communicationsignals between links 112 and 122. Furthermore, the network 130 can selfrepair upon sensing a failure of the normal communication path withinthe network 130 by establishing a restoration communication path.

The data terminals 110 and 120 transmit/receive communication signalsto/from the network 130 over their respective links 112 and 122. Thedata terminals 110 and 120 can be any one of a number of different typesof data terminals, such as computers, routers, SONET terminals, ATMswitches, cellular phones, satellites, storage devices, or anycombination of software and hardware capable of generating, relaying andrecalling from storage any information capable of being transmitted tothe network 130. Furthermore, the data terminals 110 and 120 can be anynumber of different types of data receivers capable of receiving digitalinformation such as digital computers, routers such as backbone routers,distribution routers and access routers, SONET terminals, ATM switches,cellular phones, satellites, storage mediums, transceivers, or any otherknown or later developed combination of hardware and software capable ofreceiving, relaying, storing, sensing or perceiving informationtransmitted from the network 130.

The links 112 and 122 can be any known or later developed device orsystem for connecting the data terminals 110 and 120 to the network 130.Such devices include direct serial/parallel cable connections, satellitelinks, wireless links, optical links, connections over a wide areanetwork or a local area network, connections over an intranet,connections over the Internet or connections over any other distributedprocessing network or system. Additionally, the links 112 and 122 can besoftware devices linking various software systems. In general, the links112 and 122 can be any known or later developed connected systems,computer programs or structures usable to connect the data terminals 110and 120 to the network 130.

In operation, the data terminals 110 and 120 can provide variouscommunication signals to each other. The various communication signalscan contain various different types of information such as videoinformation, audio information, web page information, digital files ofvarious sizes and the like. To enable communication, the network 130 canform a communication path by receiving a request by one or both of thedata terminals 110 and 120, reserving appropriate internal networkresources and enabling the reserved resources to form an operationalcommunication path.

However, during operations, communication paths within the network 130can occasionally fail. Upon such failures, the network 130 can quicklyself-repair by establishing new internal communication paths. Therestoration process starts as the network 130 detects a problem usingvarious fault detection devices (not shown) within the network. Upondetection of a problem, the network 130 reroutes communication from thefailed internal communication path to a new communication path withinthe network 130, thereby restoring communication.

FIG. 2 is a block diagram of an exemplary circuit switched network 1130having a set of communication nodes 1200–1218 interconnected through aseries of transmission lines 1250–1272. The communication nodes1200–1218 all communicate with and are controlled by centralizedcontroller 1220 via links 1274–1282. The centralized controller 1220sets up and reconfigures pathways within the network.

Thus, the network 1130 depends on route information being forwarded andhandled by centralized controller 1220. The network 1130 therefore isconstrained by the speed at which network controller 1220 can set upcommunications paths. In addition, the network 1130 is limited by thenumber of communications nodes that centralized controller 1220 canadminister.

The network 1130 uses a “layered” hierarchy of subsystems with thehighest layers relating to various tasks such as connectivity managementand the lowest layers relating to the hardware that provides thephysical conduits that carry various communication signals.

Connectivity management generally addresses the high level organizationand monitoring of network resources. Connectivity management can includequality of service tasks, provisioning, packet routing and bandwidthreservation. Quality of Service (QOS) can include monitoring the timethat a communication signal, or message, takes to reach a destination,and the number of communication signals that are lost in transit.Provisioning can include reserving bandwidth for future communicationsand enabling the internal pathways, when desired. Bandwidth reservationcan include reserving certain wavelengths of light or certain portionsof a circuit to accommodate a particular message.

Within the context of Internet communications, connectivity managementis based on a communication standard known as Internet Protocol (IP)which “resides” on a number of intermediate and low-level layers,including a hardware layer composed of various communication pipes suchas fiber-optic cables and the like, interconnected by special devicescalled routers.

Unfortunately, networks with multiple autonomous layers are subject toproblems such as duplication of work and scheduling conflicts due toill-coordinated distributed processing between different technologylayers.

For example, each individual layer of a conventional IP communicationsystem typically only communicates with the layers directly above orbelow, i.e., the highest layers are detached from the lowest layers. Oneeffect of this organization is that an IP layer of a conventional IPcommunication system cannot directly access information relating to thehealth of an individual communication signal. As a result, substantialdelays can result in an IP layer recognizing that individualcommunication signals are lost or corrupted.

Compounding this, complex escalation processes must be introduced toensure that multiple layers do not simultaneously react to the samefault information. For example, long timeout periods are introduced intoIP in the event of a failure to allow for restoration to occur in lowerlayer technologies.

However, by using a smart router simple optics (SRSO) approach, whichconcentrates resource management decision making and intelligence in theIP router, resource management is simplified, conflicts are eliminatedand the optical switch controller is reduced to a simple set of commandinterpreters, or drivers, called an application programming interface(API).

Another benefit to the SRSO approach is that information from the lowestnetwork layers can be easily provided to the IP and other high-levellayers to enable the high-level layers to quickly restore lost orcorrupted communication signals. For example, in a conventional IPenvironment, the health of a signal sent to a receiving terminal must beverified by either the receiving terminal or by the lowest networklayers. If the signal is lost or corrupted in transit, the IP layer mustbe notified by the receiving terminal or indirectly through five or moreother network layers that relay the information one layer to the next.Either process can take excessive amounts of time.

However, the SRSO approach enables various routers along a networkcommunication path to monitor the communication signal in transit andenable the lowest network layers to directly inform the IP or otherhigh-level layer of a lost or corrupted signal. The IP is then allowedto immediately reroute or otherwise restore the communication signal,achieving restored connectivity in substantially less time.

Table 1 below is a breakout of the different functions processed by thecontroller 1220 and by other network technologies. The various entriesof Table 1 relate to different functions within a network, rankedgenerally from highest to lowest, and include: 1) connectivitymanagement; 2) addressing; 3) traffic engineering; 4) connectionmanagement; and 5) physical switching.

TABLE 1 Centralized Function OXC Controller IP ATM POTS ConnectivityManagement X (Highest) Quality of Service X X X Packet Forwarding X XRouting X X X Addressing X X X Traffic Engineering X X X PathUtilization X X X Path Capacity X X X Topology & Resource X X X XDiscovery Provisioning X X X Bandwidth reservation X X X LocalConnection X Management Exception Handling X X Drop/Retransmitting X XRestoration X X Physical Switching X WDM/DWDM (Lowest) X

As shown in Table 1, the nodes (OXC) 1200–1218 have sole proprietorshipof the lowest level services such as physical switching and localconnection management. Physical switching, the lowest layer of layers,generally relates to controlling and monitoring a lower hardware layer(not shown) in a network to accommodate the physical transference ofinformation from a first imput port of a first MDM to a second outputport of a second MDMs.

Also shown in Table 1, the controller 1220 and IP, ATM and Plain OldTelephone (POTS) controllers have concurrent control of severalfunctions, including: addressing, traffic engineering and connectionmanagement. The first/lowest exemplary functions, can include bothexception handling, retransmission of dropped or garbled of data andrestoration of partially corrupted or lost information. The next set ofintermediate functions, traffic engineering, generally relates totracking the existence of a given path, path utilization, path capacity,topology and resource discovery. The third intermediate set offunctions, addressing, relates to high level routing, i.e., determining,as opposed to implementing, an appropriate path for a particular opticalsignal or set of packets.

As discussed above, various drawbacks arise due to thedistributed/overlapping processing shared between the controller 1220and IP/ATM/POTS controllers, especially in light of the differentpolicies and service objectives behind the various controllers. Forexample, because the controller 1220 and IP/ATM/POTS have concurrentcontrol over addressing and traffic engineering, the controller 1200 andthe nodes 1200–1218 can simultaneously determine two differentrestoration techniques to transfer a particular message. As a result,the controller 1220 must subsequently arbitrate as to which of therestoration techniques to use. Furthermore, having to independentlydetermine connectivity (paths) at different layers can result ininefficient use of network resources.

FIG. 3 is a block diagram of an exemplary network 130 having a set ofcommunication nodes 200–218 interconnected through a series oftransmission lines 250–272. While FIG. 3 depicts a network with tencommunication nodes 200–218, it should be appreciated that the size of anetwork is not important and networks of any size can be used withoutdeparting from the spirit and scope of the present invention.

The communication nodes 200–218 of the exemplary network 130 arecommunications nodes having optical-cross-connect (OXC) devices and IProuters capable of passing communication traffic to/from othercommunication nodes 200–218 via transmission lines 250–272 and tolocations external to the network 130. However, communication nodes200–218 alternatively can be any one of a number of different types ofdata nodes, such as computers, routers, including backbone, access anddistribution routers, SONET terminals, ATM switches, cellular phones,satellites, storage devices, or any other known or later developedcombination of software and hardware capable of generating, relaying,recalling from storage/storing any information capable of beingtransmitted over the network 130.

Accordingly, transmission lines 250–272 can be any known or laterdeveloped device or system for connecting the various communicationnodes 200–218. Such devices can include direct serial/parallel cableconnections, satellite links, wireless links, optical links, connectionsover a wide area network or a local area network, connections over anintranet, connections over the Internet, connections over any otherdistributed processing network or system or any other known or laterdeveloped connected systems, computer programs or structures usable toconnect the various nodes 200–218. However, for the example below, thetransmission lines 250–272 are a combination of optical links carryingwavelength division multiplexed (WDM) and dense wavelength divisionmultiplexed (DWDM) optical signals.

Furthermore, while the exemplary network 130 depicts the transmissionlines 250–272 as single communication paths, it should be appreciatedthat each transmission line 250–272 can be a single optical fiberindependently transmitting a large number of optical communicationsignals in the same direction or in opposite directions using a WDM orDWDM scheme, or the transmission lines 250–272 can be any number ofindependent optical fibers capable of transmitting large numbers ofindependent optical communication signals.

As shown in FIG. 3, communication nodes 200 and 208 are connected tolinks 112 and 122; respectively, making communication nodes 200 and 208end nodes for the purpose of this example. These end nodes 200 and 208can optionally transform outgoing optical communication signals toelectrical signals suitable for transmission over links 112 and 122, andlikewise can transform incoming electrical signals to optical signalssuitable for transmission throughout the network 130.

In normal operation, network 130 can pass various communication signalsacross the network 130. The communication signals can be eitherunidirectional (one way) or bi-directional (two way) and be of variousbandwidths. For example, a video feed could require a sustainedsingle-direction high-speed internal path, a telephony link can requirea sustained low-rate, bi-directional path and a series of web-pagetransfers can require a number of short-lived one-way paths.

Thus, the present invention provides a distributed approach for managingcommunication pathways. Each communications node has the ability tocooperate through IP protocols with other communications nodes tocontrol the network. Each communications node cooperates with othercommunications nodes so the network effectively handles thecommunications traffic. The first communications node to receive apathway setup request then selects a route through the network and sendsrequests to each node concerned. These nodes provide the desiredconnectivity where possible. Thus, the network can grow to any sizenecessary.

Communication paths are formed in the network 130 as a cooperativeeffort among the various nodes 200–218 in accordance with the InternetProtocol (IP) communication standard. As discussed above, the exemplarynetwork has two functional areas. The first functional area of theexemplary network 130 consists of various hardware components includingthe communication nodes 200–218 and transmission lines 250–272. Thesecond functional area includes an IP software/firmware device operatingin the various communication nodes 200–218 to actively manage thetopology of the network 130.

Thus, the IP software/firmware device has knowledge of the physicalresources, and how they are being used. The IP software/firmware thuscan allocate those resources in more advantageous ways and allow forfaster error recovery.

Creating a communication path can start with the IP device receiving atransfer/routing request for a particular communication signal orreceiving any other information relating to a routing request.Accordingly, the various communication nodes 200–218 will cooperate totransfer the communication signal by determining an appropriatecommunication path, scheduling and reserving the resources necessary toaccommodate transfer of the communication signal and enabling thereserved resources.

The various communication nodes 200–218 can cooperate by each nodesending out network topology and resource discovery signals. Topologyand resource discovery is implemented using Internet Protocols (IP),Open Shortest Path first (OSPF), Border Gateway Protocol (BGP) orIntermediate Systems-Intermediate Systems signals (IS-IS) as are wellknown in the art. The network topology discovered can then be used inconjunction with other information about the physical status of thenetwork to determine a route. The physical status of the network caninclude bandwidth currently in use or any other information known in theart.

For example, in order to pass information between links 112 and 122, oneof the end nodes 200 or 208 can receive a routing request from one ofthe links 112 and 122. The receiving end node 200 or 208 can thendetermine an appropriate path through the networks and forward therouting request to the nodes. The various nodes 200–218 can thencoordinate to determine a suitable path, reserve portions of theirinternal resources to enable the determined communication path andfinally enable the reserved path to pass the requested information. Therouting request can be forwarded using any known signaling scheme, suchas signaling via IP packets, Resource Reservation Protocol (RSVP) andConstraint Based Routing-Label Distribution Protocol (CR-LDP).

In this example, links 112 and 122 are connected by a normalcommunication path (shown in bold) passing along communication nodes200–202-204–206–208. End node 200 receives communication signals from adata terminal over link 112 and routes the communication signalsdirectly to node 202 and indirectly to nodes 204, 206 and 208 where itis then passed to link 122. Likewise, end node 208 receivescommunication signals from a second data terminal over link 122 androutes the communication signals directly to node 206 and indirectly tonodes 204, 202 and 200 where it is then passed to link 112.

It should be appreciated that other communication signals can besimultaneously scheduled and transported across the network 130. Forexample, a remote telephone (not shown) associated with node 210 mayneed to communicate with a telephone network (not shown) associated withnode 204. Accordingly, the network 130 can form a dedicatedbi-directional path between nodes 204 and 210 by coordinating,scheduling, reserving and enabling the necessary resources to passvarious telephony signals.

In order to coordinate resources and provide communication paths, thevarious communication nodes 200–218 transmit, relay and receive statusinformation and commands to each other and perform various diagnostics.For example, node 200 can transmit information directly to node 202 andindirectly to nodes 204, 206 and 208 over a pre-designated opticalfrequency to discover network topology and resource states, to establisha communication path or to inform the other nodes 202–218 that node 200detected a failure in a received communication signal.

A second function of the network is to self-diagnose various errorconditions, including low-level and high-level error conditions, and todynamically adjust the workings of the network accordingly.

The first type of error detection, i.e., low-level error detection, isprovided using error detection circuitry in the nodes 200–218 that candiagnose the various hardware, and otherwise detect errors incommunication signals as they are routed throughout the network 130. Thetypes of error conditions that can be measured by the nodes 200–218include detection of the presence of various laser carriers receivedfrom each transmission line 250–272 as well as errors incorporatedwithin communication signals such as single bit errors, octet errors,cyclic redundancy check (CRC) errors, checksum errors, framing errorsand loss of signal errors. However, as communication standards evolveand new standards develop, it should be appreciated that any errorcondition or failure capable of being measured can be used withoutdeparting from the spirit and scope of the present invention.

As every physical communication system can occasionally produceoccasional errors, a determination can be made as to what kind of errorsof any given class of errors is acceptable. For example, three or foursingle bit errors per second may be an acceptable error condition forsome communication signals such as a video stream, yet a singlebit-error may be unacceptable for other applications such as a web-filetransfer. As different error conditions and failures can occur forvarious environments having different requirements, it should beappreciated that any measure of acceptable and unacceptable errorconditions can be used as may be required by design.

As discussed above, as the various low-level error conditions aredetected, the error conditions may be communicated to the IP layer. Invarious embodiments, low-level error conditions detected by the hardwareof the various nodes 200–218 can directly provide information relatingto the error conditions to the IP and other high-level layers withoutrequiring handling by any intermediate layer. However, it should beappreciated that information relating to the various error conditionscan alternatively be indirectly provided to the IP or other high-levellayers indirectly through one or more intermediate layers as required bydesign.

In addition to low-level error detection, error conditions can bedetected directly by the IP and/or other high-level layer. For example,each of the nodes 200–218 can determine whether the various transmissionlines 250–272 and the other nodes are functional by periodically“pinging” the other nodes. A “ping” is any communication signal where afirst device can detect the presence of a second device. Typically,“pings” are short communication signals containing little or noinformation, but still require a receiving device to send anacknowledgment signal to the “pinging” device. Alternatively, a “hello”that is not acknowledged by the receiving node can be used.Alternatively, messages can be sent independently from both ends.Patterns of lost or corrupted messages can be used to indicate afailure. Accordingly, a first device can verify the existence of aworking second device as well as a functional bi-directional path by“pinging” the second device, or having the second device sending aperiodic “hello”.

The nodes of the exemplary network 130 ping each other during times justbefore and during periods when an active path connects the nodes. Forexample, to assure connectivity for the normal path 200–202–204–206–208,each of the normal path nodes 200–208 can ping their nearest neighborsalong the normal path 200–202–204–206–208 just before the path isestablished and can further ping each other for the duration of thepath's existence.

Alternative to the nearest neighbor approach, other connectivityapproaches can be used including: (1) requiring each of the nodes200–208 along the normal path 200–202–204–206–208 to ping all othernormal path nodes 200–208; (2) requiring only each of the end nodes 200and 208 to ping the other normal path nodes 202–208 or 200–206; or (3)requiring each of the end nodes 200 and 208 to ping only the other endnode 200 or 208. Pings can occur between any two given nodes duringregular network operation or the nodes can ping each other only duringdesignated times.

The exemplary network 130 uses a nearest neighbor approach where eachnode pings its neighbors at a rate of 2,000 pings per second to providefailure detection in about 1000th of a second. However, it should beappreciated that the ping rate will be a design choice as required bythe particular requirements of a given network.

In the event one of the communication nodes 202–208 or transmissionlines 250–256 along the normal communication path fails or are otherwisedetermined to have an unacceptable error condition, the network 130 canself-repair by establishing restoration communication paths.

An exemplary method for restoring the network is that the communicationnode first attempts to correct the error within the communication node.Thus, if a laser failed within a communications node, the node mayactivate a backup laser, or switch the communications to a functioningbut not currently in use laser alternately the communications node IPlayer can send packets out on another interface, without changing anyoptical connectivity.

Next the communications node may attempt to correct the error byalerting those nodes that transmit significant data. Those nodes may beable to reroute either the information that is now being interrupted, ormay allow the transmission of the data by rerouting other data such thatcommunications resources are freed up.

Next the communications node may attempt to correct the error by sendinga general alert to the entire communications network such that thenetwork may reroute traffic around a failed pathway or node.

FIG. 4 shows an example of the network 130 of FIG. 2 after a completefailure occurred on transmission line 254 of the normal communicationpath. If the failure is unidirectional, only the downstream nodes206–208 receiving the failed signal can sense the loss of signal and caninform the nodes 200–202 of the failure. However, if the failure isbi-directional, the failure can be sensed by the hardware of all nodes200–208 along the transmission path 200–202–204–206–208, andsubsequently, any of the communication nodes 200–208 along thetransmission path 200–202–204–206–208 can inform the other nodes of afailure. Furthermore, if the various nodes 200–218 along the normal pathare pinging one another, the nodes can directly receive informationrelating to a high-level connectivity error condition.

Immediately upon directly or indirectly detecting a failure, an IProuter in either node 204 or node 208 can perform restoration byredirecting traffic away from a failed element using either apre-computed or post-computed alternate route. As shown in FIG. 3, a newcommunication path, or restoration path, between nodes 200 and 208bypasses the failed link 254.

As with determining an initial communication path, determining arestoration path requires the IP software/firmware layer operating inthe various nodes 200–218 to actively manage the connectivity of thenetwork 130. Accordingly, during restoration, the various nodes 200–218can coordinate to determine a suitable restoration path accounting forthe failed transmission line 254 and any other error conditions, reserveportions of their internal resources to enable the determinedrestoration communication path and finally enable the reservedrestoration path to reroute information.

As shown in FIG. 4, an exemplary restoration path can consist of nodes200–202–204–218–208. However, as is evident in FIG. 4, the exemplarynetwork 130 can create a variety of restoration paths. Accordingly, itshould be appreciated that the restoration path can be determined basedon the same criteria as the original communication path accounting forvariables such as other existing traffic, bandwidth capacity ofindividual nodes, various error conditions and the like.

FIG. 5 shows a block diagram of an exemplary communications node 400using a smart router simple optics (SRSO) approach. The communicationsnode 400 includes an IP router 464, a first optical/electrical interface(OEC) 460, a second optical/electrical interface (OEC) 470, anapplication programming interface (API) 466, an optical-cross-connectswitch (OXC) and a first and second multiplexer/de-multiplexers (MDM)420 and 440. The first MDM 420 is connected to a first group oftransmission lines 411–414 and the second MDM 440 is connected to asecond group of transmission lines 451–454.

In operation the first and second MDMs 420 and 440 receive various typesof signals. Some signals are directed to a respective OEC 460 or 470 vialinks 421 or 441. Other signals from the OECs 460 or 470 can provide thereceived signals to the various external transmission lines 411–414 or451–454. Other information not passed between one of the OECs 460 or 470can be passed to/from the OXC 430 via links 422–424 and 442–444.

The OXC can pass signals out to MDM 420 or 440 or the OECs 460 or 470.Thus control information can be passed on a dedicated wavelength assegregated by the MDMs 420 and 440, or control information can be passedon a service data wavelength for segregation by the OXC 430.

In various exemplary embodiments, the MDMs 420 and 440 are a collectionof optical components. However, it should appreciated that the MDMs 420and 440 can be any known or later developed device or system that canreceive signals, including WDM optical signals, from transmission lines411–414 and 451–454 and direct the signals to the OXC 430 and/or theOECs 460 and 470.

Accordingly, the exemplary transmission lines 411–414 and 451–454 can besingle-mode optical fibers transmitting a number of WDM optical signals.However, it should be appreciated that the transmission lines 411–414and 451–454 can be any known or later developed device or system thatcan transport signals to and from the various MDMs 420 and 440 such as agigabit Ethernet device, an Asynchronous Transfer Mode device, a SONETDevice and the like.

The OECs 460 and 470 can receive optical signals from the MDMs 420 and440 or the OXC 430 via links 421 and 441, convert the optical signals toan electrical form, and pass the converted signals to the IP router 464using links 459, 471 and 473. The OECs 460 and 470 can also receiveelectrical signals from the IP router 464 using links 459 and 471,convert the electrical signals to an optical form, and pass theconverted signals to the MDMs 420 and 440 via links 421 and 441.

The exemplary links 421 and 441 are single-mode optical fiberstransmitting a number of optical signals. However, it should also beappreciated that the links 421 and 441 can be any known or laterdeveloped device or system that can transfer signals, including WDM andDWDM optical signals, between the MDMs 420 and 440 and the OECs 460 and470.

The IP router 464 can receive various communication signals such asrouting requests, data files and data streams from the OECs 460 and 470.If a message/routing request relates to the IP protocol, the IP router464 can determine appropriate paths to transfer information.

Upon reception of a signal, the IP router 464 can either transfer thefiles directly or determine an appropriate path in the OXC 430. Forexample, if the IP router 464 receives a request to transfer a file suchas a web page from a first WDM channel λ₁ on transmission line 411 to asecond WDM optical channel λ₂ on transmission line 451, the first MDM420 can route the file data to the IP router 464 using the first OEC 460and links 459 and 421. The IP router 464 can subsequently direct thesecond MDM 440 to receive the file using the second OEC 470 and links441 and 471 and transmit the file to optical channel λ₂ on transmissionline 451.

Alternatively, if the IP router 464 can direct the first MDM 420 toprovide the first WDM channel λ₁ to the OXC 430, reserve and enable apath in the OXC 430 to provide a connection between the two MDMs 420 and440, and direct the second WDM 440 to receive the appropriate signalfrom the OXC 430 and provide the signal to channel λ₂ to transmissionline 451.

If the IP router 464 uses the OXC 430 to complete a connection, the IProuter 464 first commands the MDMs 420 and 440 to route thecommunication signals to/from the transmission lines 411–414 or 451–454and the OXC 430, and sends commands to the API 466 to configure the OXC430 accordingly.

As discussed above, the API 466 is a basic set of drivers that canreceive connection commands and configure the OXC accordingly. The APIcan exist either as part of the IP router 464 or as part of the OXC 430.For the example above, in order to transfer a signal on first WDMchannel λ₁ on transmission line 411 to the second WDM channel λ₂ ontransmission line 451, the API 466 can receive a command containing anumber of arguments over links 463 or 465 relating to the source anddestination channels, the required bandwidth, and various otherarguments relating to safeguarding a reserved path and enablinginterrupts. Once the API 466 receives the command, the API 466 canappropriately configure the OXC 430 using link 484 to receive acommunication signal from one of the links 422–424 or 442–444 andprovide the communication signal to one of the other links 422–424 or442–444.

Besides executing commands, the exemplary API controller 466 can monitorthe OXC 430 and pass various information such as communication signalstatus and the error conditions to the IP router 464. Status and errorcondition information can include information such as the presence orabsence of a laser carrier signal on any given transmission line as wellas status relating to communication signals received from the varioustransmission lines 411–414 or 451–454 such as single bit errors, octeterrors, cyclic redundancy check (CRC) errors, checksum errors, framingerrors and loss of signal errors. However, as discussed above, ascommunication standards evolve and new standards develop, it should beappreciated that any error condition or failure capable of beingmeasured can be used without departing from the spirit and scope of thepresent invention.

The IP router 464 is microprocessor-based device having variousperipheral devices. However, it should be appreciated that the IP router464 can be any known or later developed combination of hardware andsoftware that can receive and transmit communication signals from theOEC 460 and 470, issue commands to the API 466 and receive status anderror condition information from API 466 such as a digital signalprocessor, a micro-controller, a combination of various logic circuitsand discrete hardware, and the like.

The exemplary API 466, like the IP Router 464, is a microprocessor-baseddevice having various peripheral devices. However, it should beappreciated that the exemplary API 466 can be any known or laterdeveloped combination of hardware and software that can receive commandsfrom an IP or other controller and configure and monitor an OXC such asa digital signal processor, a combination of various logic circuits anddiscrete hardware and the like.

Accordingly, in various exemplary embodiments, the OXC 430 is acollection of optical and electrical components. However, it shouldappreciated that the OXC 430 can be any known or later developed deviceor system that can receive optical signals from the MDMs 420 and 440,redirect the optical signals under control of the API 466 and providestatus and error condition information to the API 466.

Table 2 below is a breakout of the different tasks processed by the IProuter 464 and the API 466. As with Table 1, Table 2 relate to thedifferent layers within a network including: 1) connectivity management;2) addressing; 3) traffic engineering; 4) connection management; and 5)physical switching. However, as shown in Table 2, the various layers aredifferently assigned between the various controllers 462, 464 and 466.

TABLE 2 1) Connectivity Management (Highest) Quality of ServiceBandwidth reservation 2) Addressing Routing 3) Traffic Engineering PathExistence IP Path Utilization Path Capacity Topology & Resource Recovery4) Connection Management Exception Handling Drop/RetransmittingRestoration 5) Physical Switching OXC/API WDM/DWDM (Lowest)

As shown in Table 2, the IP router 464 is responsible for all higherfunctions, including connection management, traffic engineering,addressing, and connectivity management. The IP router is responsiblefor all logical and physical resources. The API 466 and the OXC 430 arerelegated to the physical switching tasks such as providing capacity,local dynamic connectivity and other transparent optical services forWDM and DWDM optical links.

One benefit of allocating tasks according to Table 2 is that the API 466can be reduced to a simple set of command interpreters/drivers. Otherbenefits to concentrating decision making and intelligence in the IProuter 464 include simplifying resource management, eliminatingconflicts and enabling faster recognition of status and error conditioninformation by an IP router. The benefits provided to users accordinglyinclude faster connection and restoration speeds.

For example, during an initial connection, the IP router 464 can receivecommunication signals relating to a routing request for a particularcommunication signal and determine a viable communication path withinthe OXC 430 without the possibility of resolving conflicts that canarise when other decision-making devices make parallel decisions.Similarly, during a restoration operation, the IP router 464 is free toreroute communication signals without conflict.

Still another benefit is that, because more network layers are handledby a single controller, signals originating at the lower levels can bepassed directly to the upper layers without requiring that the signalspass through intermediate levels. For example, status and errorinformation provided by the physical switching layer can be directlyaccessed by the connectivity management layer, without requiringtime-consuming handling by the addressing, traffic engineering andconnection management layers.

FIG. 6 is a flowchart outlining an exemplary method for formingcommunication paths in a network using a router having a circuitswitched device and a packet switched device. The operation starts instep 710 where the communications node receives a communication signal.In step 720 a determination is made whether the signal arrived on achannel that is terminated at the IP router (packet switched device). Ifthe signal arrived on a data channel terminated at the router, controlcontinues to step 730. Otherwise control jumps to step 770.

In step 770 the signal is forwarded to the pre-designated output portwithout further interpretation. Thus, the method allows for rapidforwarding of information that does not require interpretation by thepacket switched (IP router) device.

Next, in step 730, a determination is made as to whether thecommunication signal is a control signal to establish a communicationpath for a particular communication signal. If the message is not acontrol signal, control continues to step 740; otherwise, control jumpsto step 780. In step 780 control jumps to step 800.

In step 740, a determination is made whether the data is service data.If the data is service data, control jumps to step 790. Otherwisecontrol continues to step 750.

In step 750, a determination is made whether to continue. If the node isto continue, control jumps back to step 710 where the next communicationsignal is received; otherwise, control continues to step 760 where theoperation stops.

In FIG. 7, control starts at step 800. In step 800 the destination forthe signal is analyzed. Control then continues to step 810.

In step 810, a determination is made whether the destination is local,or that the signal will not travel in the network. Therefore, since thesignal will only be traveling within the communications node, nocommunications with other nodes is necessary. If the destination islocal, control jumps to step 880, otherwise control continues to step820.

In step 880, the OXC is configured to carry signals along the pathrequested by the first signal. Control then continues to step 870.

In step 820, a communication path is determined to pass thecommunication signal, including a path in the node's OXC. As discussedabove, the exemplary operation uses an IP router that handles severaldifferent layers within a network, including: 1) connectivitymanagement; 2) addressing; 3) traffic engineering; and 4) connectionmanagement. Control continues to step 830.

In step 850, the bandwidth requests are sent to downstream nodes.Control then continues to step 840.

In step 840, a determination is made whether the bandwidth is availablethrough the entire network based on responses from other communicationnodes. If the bandwidth is available, control continues to step 850,otherwise control jumps to step 890.

In step 890 a determination is made whether alternate paths areavailable within the network. If other paths are available, controljumps back to step 820, otherwise control continues to step 900. In step900, request failure is sent.

In step 850, the internal communication node OXC is configured. Controlcontinues to step 860.

In step 860, routing configuration commands are sent to the othercommunications nodes that will be involved in the path. Control thencontinues to step 810. In step 870 control jumps to B in FIG. 6.

As shown in FIG. 5, the systems and methods of this invention arepreferably implemented on a digital signal processor (DSP) with variousintegrated electrical and optical circuits. However, the systems andmethods can also be implemented using any combination of one or moregeneral purpose computers, special purpose computers, programmedmicroprocessors or microcontrollers and peripheral integrated circuitelements, hardware electronic or logic circuits such as ApplicationSpecific Integrated Circuits (ASIC), discrete element circuits,programmable logic devices such as a PLD, PLA, FPGA, or PAL, or thelike. In general, any device on which exists a finite state machineand/or various optical interfaces capable of implementing the variouselements of FIG. 5 and the flowchart of FIGS. 6 and 7 can be used toimplement the communications node functions.

While this invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, the preferred embodiments of the invention as set forthherein are intended to be illustrative, not limiting. Various changesmay be made without departing from the spirit and scope of theinvention.

1. A communications node, comprising: a packet switched device thatoperates using Internet Protocol, wherein the packet switched devicemanages communication resources; and a circuit switched device thatprovides physical switching between a plurality of ports based on one ormore commands from the packet switched device, wherein: the circuitswitched device can provide at least one error condition to the packetswitched device, and the packet switched device issues instructions tothe circuit switched device to handle the at least one error.
 2. Acommunications node, comprising: a packet switched device that operatesusing Internet Protocol, wherein the packet switched device managescommunication resources; and a circuit switched device that providesphysical switching between a plurality of ports based on one or morecommands from the packet switched device, wherein: the circuit switcheddevice can provide at least one error condition to the packet switcheddevice, and the packet switched device issues instructions to thecircuit switched device to handle the at least one error; and the errorcondition is a pattern of lost or corrupted data.
 3. A communicationsnode, comprising: a packet switched device that operates using InternetProtocol, wherein the packet switched device manages communicationresources; and a circuit switched device that provides physicalswitching between a plurality of ports based on one or more commandsfrom the packet switched device, wherein: the circuit switched devicecan provide at least one error condition to the packet switched device,and the packet switched device issues instructions to the circuitswitched device to handle the at least one error; and the packetswitched device sends either instructions or notifications to at leastone other communications node to handle the error.
 4. A communicationsnode, comprising: a packet switched device that operates using InternetProtocol, wherein the packet switched device manages communicationresources; and a circuit switched device that provides physicalswitching between a plurality of ports based on one or more commandsfrom the packet switched device, and wherein the packet switched devicesends signals to determine at least one error condition and issuesinstructions to the circuit switched device to handle the at least oneerror.
 5. A communications node, comprising: a packet switched devicethat operates using Internet Protocol, wherein the packet switcheddevice manages communication resources; and a circuit switched devicethat provides physical switching between a plurality of ports based onone or more commands from the packet switched device, and wherein thepacket switched device sends signals to determine at least one errorcondition and issues instructions to the circuit switched device tohandle the at least one error; and the packet switched device sendseither instructions or notifications to at least one othercommunications node to handle the error.
 6. A communications node,comprising: a packet switched device that operates using InternetProtocol, wherein the packet switched device manages communicationresources; and a circuit switched device that provides physicalswitching between a plurality of ports based on one or more commandsfrom the packet switched device, and wherein: the packet switched devicehandles at least one of managing peer interfaces, managing externalinterfaces, managing internal resources, managing faults, and managinginternal faults at the network edge; and the packet switched device usesat least one of interior or exterior protocols, Border Gateway Protocol,Open Shortest Path First and Intermediate Systems-Intermediate Systemssignals to discover a network topology.
 7. A communications node,comprising: a packet switched device that operates using InternetProtocol, wherein the packet switched device manages communicationresources; and a circuit switched device that provides physicalswitching between a plurality of ports based on one or more commandsfrom the packet switched device, and wherein: the packet switched devicehandles at least one of managing peer interfaces, managing, externalinterfaces, managing internal resources, managing faults, and managinginternal faults at the network edge; the packet switched device uses atleast one of interior or exterior protocols, Border Gateway Protocol,Open Shortest Path First and Intermediate Systems-Intermediate Systemssignals to discover a network topology; and the packet switched deviceuses at least one of the network topology and a bandwidth in use indetermining the one or more commands.
 8. A communications node,comprising: a packet switched device that operates using InternetProtocol, wherein the packet switched device manages communicationresources; and a circuit switched device that provides physicalswitching between a plurality of ports based on one or more commandsfrom the packet switched device, and wherein: the packet switched devicehandles at least one of managing peer interfaces, managing externalinterfaces, managing internal resources, managing faults, and managinginternal faults at the network edge; the packet switched device uses atleast one of interior or exterior protocols, Border Gateway Protocol,Open Shortest Path First and Intermediate Systems-Intermediate Systemssignals to discover a network topology; the packet switched device usesat least one of the network topology and a bandwidth in use indetermining the one or more commands; and the packet switched devicesends at least one of the one or more commands to at least one othercommunications node.
 9. A communications node, comprising: a packetswitched device that operates using Internet Protocol, wherein thepacket switched device manages communication resources; and a circuitswitched device that provides physical switching between a plurality ofports based on one or more commands from the packet switched device, andwherein: the packet switched device handles at least one of managingpeer interfaces, managing external interfaces, managing internalresources, managing faults, and managing internal faults at the networkedge; the packet switched device uses at least one of interior orexterior protocols, Border Gateway Protocol, Open Shortest Path Firstand Intermediate Systems-Intermediate Systems signals to discover anetwork topology; the packet switched device uses at least one of thenetwork topology and a bandwidth in use in determining the one or morecommands; the packet switched device sends at least one of the one ormore commands to at least one other communications node; and the atleast one of the one or more commands is sent to the at least one othercommunications node using at least one of signaling via IP packets,resource reservation protocol (RSVP) and Constraint Based Routing-LabelDistribution Protocol (CR-LDP).
 10. A method for providing communicationpaths in an Internet Protocol network environment, comprising:determining, using a packet switched device, how to managecommunications resources; providing physical switching using a circuitswitched device between a plurality of ports based on the one or morecommands, and further comprising the steps of: providing at least oneerror condition to the packet switched device; and issuing instructionsfrom the packet switched device to the circuit switched device to handlethe at least one error.
 11. A method for providing communication pathsin an Internet Protocol network environment, comprising: determining,using a packet switched device, how to manage communications resources;providing physical switching using a circuit switched device between aplurality of ports based on the one or more commands, and furthercomprising the steps of: providing at least one error condition to thepacket switched device; and issuing instructions from the packetswitched device to the circuit switched device to handle the at leastone error, wherein the issuing of instructions includes sending eitherinstructions or notifications to at least one other communications nodeto handle the error.
 12. A method for providing communication paths inan Internet Protocol network environment, comprising: determining, usinga packet switched device, how to manage communications resources;providing physical switching using a circuit switched device between aplurality of ports based on the one or more commands, and furthercomprising the steps of: sending signals from the packet switched deviceto determine at least one error condition; and issuing instructions tothe circuit switched device to handle the at least one error.
 13. Amethod for providing communication paths in an Internet Protocol networkenvironment, comprising: determining, using a packet switched device,how to manage communications resources; providing physical switchingusing a circuit switched device between a plurality of ports based onthe one or more commands, and further comprising the steps of: sendingsignals from the packet switched device to determine at least one errorcondition; and issuing instructions to the circuit switched device tohandle the at least one error, wherein the error condition is a patternof lost or corrupted data.
 14. A method for providing communicationpaths in an Internet Protocol network environment, comprising:determining, using a packet switched device, how to managecommunications resources; providing physical switching using a circuitswitched device between a plurality of ports based on the one or morecommands, and further comprising the steps of: sending signals from thepacket switched device to determine at least one error condition; andissuing instructions to the circuit switched device to handle the atleast one error, wherein the issuing of instructions includes sendingeither instructions or notification to at least one other communicationsnode to handle the error.
 15. A method for providing communication pathsin an Internet Protocol network environment, comprising: determining,using a pack switched device, how to manage communications resources;and providing physical switching using a circuit switched device betweena plurality of ports based on the one or more commands, wherein: thedetermining includes at least one of managing peer interfaces, managingexternal interfaces, managing internal resources, managing internalfaults, managing faults at the network edge; and the determining uses atleast one of internal or external gateway protocols, Open Shortest PathFirst (OSPF), border gateway protocol and IntermediateSystems-Intermediate Systems (IS-IS) signals to discover a networktopology.
 16. A method for providing communication paths in an InternetProtocol network environment, comprising: determining, using a packetswitched device, how to manage communications resources; and providingphysical switching using a circuit switched device between a pluralityof ports based on the one or more commands, wherein: the determiningincludes at least one of managing peer interfaces, managing externalinterfaces, managing internal resources, managing internal faults,managing faults at the network edge; the determining uses at least oneof internal or external gateway protocols, Open Shortest Path First(OSPF), border gateway protocol and Intermediate Systems-intermediateSystems (IS-IS) signals to discover a network topology; and thedetermining step uses at least one of the network topology and abandwidth in use in determining one or more commands.
 17. A method forproviding communication paths in an Internet Protocol networkenvironment, comprising: determining, using a packet switched device,how to manage communications resources; and providing physical switchingusing a circuit switched device between a plurality of ports based onthe one or more commands, wherein: the determining includes at least oneof managing peer interfaces, managing external interfaces, managinginternal resources, managing internal faults, managing faults at thenetwork edge; the determining uses at least one of internal or externalgateway protocols, Open Shortest Path First (OSPF), border gatewayprotocol and Intermediate Systems-Intermediate Systems (IS-IS) signalsto discover a network topology; the determining step uses at least oneof the network topology and a bandwidth in use in determining one ormore commands; and the packet switched devices ends one or more commandsto at least one other communications node.
 18. A method for providingcommunication paths in an Internet Protocol network environmentcomprising: determining, using a packet switched device, how to managecommunications resources; and providing physical switching using acircuit switched device between a plurality of ports based on the one ormore commands, wherein: the determining includes at least one ofmanaging peer interfaces, managing external interfaces, managinginternal resources, managing internal faults, managing faults at thenetwork edge; the determining uses at least one of internal or externalgateway protocols, Open Shortest Path First (OSPF), border gatewayprotocol and Intermediate Systems-Intermediate Systems (IS-IS) signalsto discover a network topology; the determining step uses at least oneof the network topology and a bandwidth in use in determining one ormore commands; the packet switched devices ends one or more commands toat least one other communications node; and the at least one of the oneor more commands is sent to the at least one other communications nodeusing at least one of signaling via IP packets, Resource ReservationProtocol (RSVP) and Constraint Based Routing-Label Distribution Protocol(CR-LDP).